Optical signal receiving unti and apparatus for reproducing information

ABSTRACT

The optical signal receiving unit ( 10 ), which receives and processes an optical signal, can be programmed by the optical signal. The optical signal is detected by an optical sensor ( 20 ) and processed by a signal processor ( 40 ). The signal processor ( 40 ) has an operating mode, which is set by a programmable control unit ( 30 ). The control unit ( 30 ) is programmable by a program signal derived from the optical signal. In one embodiment the optical signal receiving unit ( 10 ) can be switched between two operating modes by a program switch signal provided at a program switch terminal ( 53 ). The apparatus ( 100 ) for reproducing information from an optical data carrier ( 101 ) comprises an optical signal receiving unit ( 10 ) according to the invention.

The invention relates to an optical signal receiving unit comprising anoptical sensor for receiving optical signals, control means forproviding a control signal, and a signal processor for processing theoptical signal to produce a processed signal, the signal processorhaving an operating mode set by the control signal.

The invention also relates to an apparatus for reproducing informationfrom an optical data carrier comprising such an optical signal receivingunit.

The data sheet of the photodiode and amplifier IC for CD and DVDapplications TZA1045 by Philips Semiconductor discloses an embodiment ofan optical signal receiving unit as described in the opening paragraph.The IC comprises a photodiode, which is used as an optical sensor forreceiving an optical signal generated by a light source such as, e.g., alaser, irradiating an optical data carrier such as, e.g., a CD disc orDVD disc. The optical signal received by the photodiode is processed bya signal processor which comprises a set of amplifiers integrated in theIC. The processed signal is provided at the output terminal for furtherprocessing, e.g., in an apparatus comprising the optical signalreceiving unit such as, e.g., a CD player or a DVD player.

At present many apparatus such as CD players and DVD players are capableto reproduce information from and to record information on a datacarrier. These applications are referred to as reading and writing,respectively. For writing it is often required to monitor the light beamreflected by the optical data carrier to assure that the information isbeing recorded with the appropriate intensity and on the correct portionof the data carrier. The light may be monitored by the optical signalreceiving unit. For each application such as, e.g., reading a CD disc,writing a CD disc, reading a DVD disc and writing a DVD disc, the signalprocessor has an operating mode specific for the application. Theoperating mode comprises amongst others a set of amplification factorsfor the set of amplifiers, which are specific for the application.

The operating mode is set by a control signal, which is provided bycontrol means. In the known optical signal receiving unit this controlmeans comprises three control terminals, which receive a digital signaland provide it to a decoder. The digital signal may be provided by, e.g.a system control means of the apparatus comprising the optical signalreceiving unit. Depending on the digital signal the decoder provides acorresponding set of voltages determining the set of amplificationfactors. Because the control means comprises three binary controlterminals, a maximum of 2³, i.e. eight, different operating states canbe distinguished.

It is a disadvantage of the known optical signal receiving unit that thenumber of operation modes, which can be set by the control means, islimited by the number of control terminals. The number of applicationseach requiring an application specific operating mode is growing andtherefore, there is a need to be able to switch between an increasingnumber of operation modes.

It is an object of the invention to provide an optical signal receivingunit of the kind described in the opening paragraph in which the numberof operation modes, which can be set by the control means, isindependent of the number of control terminals.

The invention is defined by the independent claims. The dependent claimsdefine advantageous embodiments.

According to the invention the optical sensor is arranged for receivingan optical signal, which comprises an optical program signal, and thecontrol signal is dependent on the optical program signal. Theinformation required for setting the operating mode is transferred tothe optical signal receiving unit via light detected by the opticalsensor. The number of operation modes is then determined by the opticalprogram signal and not by the number of control terminals.

In U.S. Pat. No. 4,626,848 a reconfigurable remote control is disclosedthat has the ability to learn, store and repeat the remote control codesfrom any other infrared transmitter. The reconfigurable remote controltransmitter includes an infrared receiver, a microprocessor, nonvolatileand scratch pad random access memories, and an infrared transmitter. Themicroprocessor application is divided into four main categories:learning storing, retransmitting, and user interface. In the learningprocess, the reconfigurable remote transmitter receives and decodes thetransmissions from another remote control transmitter. The process isrepeated at least twice for each key to make sure that it has beenproperly received and decoded. Once the data has been received anddecoded it is stored for latter use. When the learning and storingoperations have been completed, the reconfigurable remote control isready to use as a remote control. However, it is not suited to be usedas an optical signal receiving unit.

In an embodiment the optical signal receiving unit further comprises aprogram control terminal for receiving a program control signal enablingthe control means to be programmed by a program signal derived from theoptical signal. By providing a program control signal such as, e.g., avoltage corresponding to a first digital condition, e.g., to the highcondition, at the program control terminal, the control means is set ina program mode. In this mode the information required for setting theoperating mode and comprised in the program mode is transferred to theoptical signal receiving unit via light detected by the optical sensor.In an embodiment the control signal is obtained from the program signalby integrating the optical signal over the period of time, in which theprogram control signal is present.

In another embodiment, the program control terminal is omitted and theoptical signal receiving unit further comprises program signal detectionmeans for detecting the optical program signal and for deriving aprogram signal from it. The optical program signal may be composed of asignal in a predefined frequency band, which is preferably substantiallyfree from the optical information signal in order to reduce the chanceof erroneously interchanging the optical program signal and the opticalinformation signal when programming the control means. In this case theprogram signal detection means may be, e.g., a band pass filter arrangedto transmit the optical signal within this predefined frequency band tothe control means while suppressing the optical signal outside thispredetermined frequency band. Thus, the program signal detection meansdiscriminates the optical program signal from the optical informationsignal based on the frequency of these two signals.

In a variation of this embodiment the optical program signal and theoptical information signal have an optical program amplitude and anoptical information amplitude, respectively, the optical programamplitude being different from the optical information amplitude. Here,amplitude refers to the intensity of the two signals. The program signaldetection means is an amplitude filter arranged to transmit the opticalsignal having the optical program amplitude while suppressing theoptical signal having the optical information amplitude. Thus, theprogram signal detection means discriminates the optical program signalfrom the optical information signal based on the amplitudes of these twosignals.

Alternatively, or in addition, the two signals may be discriminatedbased on different wavelengths. To this end, the wavelength of the lightsource may be varied, resulting in a varying optical signal due to,e.g., a wavelength dependent sensitivity of the optical sensor.Alternatively, the program signal may be encoded in the optical signalby the optical data carrier irradiated by the light source.

The optical signal may be processed by the signal processor before it isused as program signal.

The discriminated optical program signal may then be used to derive theprogram signal is a way similar to the embodiment having a programcontrol terminal.

It is advantageous if the control means comprises a first decoder fordecoding the program signal and providing a decoded program signal. Fora reliable programming it is advantageous if the program signal isencoded in the optical signal, e.g., by varying the light intensity of alight source used for generating the optical signal such as, e.g.,switching the light source on and off resulting in a pulsed signal. Inthis case a first, e.g. digital, decoder may be used to derive thecontrol signal from the program signal.

It is advantageous if the first decoder comprises a pulse counter. Thisis an economic means for decoding a pulsed signal. Alternatively, thefirst decoder may comprise a synchronous receiver, which is providedwith a clock signal also provided to the light source for modulating theoptical signal.

It is advantageous if the control means further comprise a memory devicefor storing and providing the decoded program signal. It is economic toprogram the control means only when it is necessary to change theoperating mode. This requires storing the decoded program signal in amemory device. Alternatively, the program signal may be continuouslyencoded in the optical signal.

It is advantageous if the memory device comprises a latch. This is aneconomic means for storing the decoded program signal. The content ofthe latch may be directly proportional to the control signal, e.g., tothe amplification factor. Alternatively, the memory device may comprisea random access memory, which is capable of storing a complex programsignal.

It is advantageous if the control means further comprises a seconddecoder for further decoding the decoded program signal provided by thememory device and for providing the control signal. In many cases thedecoded program signal provided by the memory device is not directlyproportional to the control signal. The control signal may compriseinformation about, e.g., the amplification factors of various amplifiersin the signal processor. For a more economic storage of this informationit may be advantageous not to store the control signal itself, e.g. allthe amplification factors individually, but to store a simpler digitalcode, which comprises the control signal after being decoded by thesecond decoder.

It is advantageous if the optical sensor comprises a first detector forproviding the optical signal to the signal processor and a seconddetector for providing the program signal, which is derived from theoptical signal, to the control means. The signal provided by the seconddetector may be processed, e.g. amplified, before it is used as theprogram signal.

When the optical signal receiving unit is used in an apparatus forreproducing information from an optical data carrier such as, e.g., a CDplayer or a DVD player, a light source such as, e.g., a laser is usedfor irradiating the data carrier, e.g. a CD disc or a DVD disc, togenerate an optical signal comprising the information from the opticaldata carrier. This optical signal is detected by the first detector,processed by the signal processor and provided at the output terminal.

For programming the control means it is often advantageous if theoptical signal, which is used to derive the program signal, is notdetected after being reflected or transmitted by the optical datacarrier because this may disturb the programming. Therefore, the seconddetector is used, which preferably detects the optical signal not havinginteracted with the optical data carrier. In an apparatus forreproducing information from an optical data carrier this may beachieved by directly exposing the second detector to light generated bythe light source.

It is advantageous if the optical signal receiving unit furthercomprises a monitor terminal for monitoring the program signal. Therebyit is possible to monitor the programming of the control means and torepeat the programming in case the monitored program signal does notcorrespond to the generated optical signal.

It is advantageous if the optical signal receiving unit having a memorydevice has a control means, which is able to provide a first controlsignal and a second control signal, furthermore a signal processor,which has a first operating mode set by the first control signal and asecond operating mode set by the second control signal, and a programswitch terminal for receiving a program switch signal enabling thecontrol means to switch between the first control signal and the secondcontrol signal.

In another embodiment the optical program signal comprises a power downsignal, the signal processor has a power down operating mode in whichthe signal processor is switched off, the power down operating modebeing set by the control means when the control signal depends on thepower down signal. In this case the power consumption is relativelysmall which is particularly advantageous in, e.g. mobile applicationsduring periods in which the optical signal receiving unit is not usedand the signal processor is switched off.

In one embodiment the power down signal is given by an optical signalwith an intensity integrated over a predefined period of time period,which integrated intensity is smaller than a predefined integratedintensity. In another embodiment the power down signal is given by apredefined pulse sequence.

This optical signal receiving unit may be used in an apparatus forreproducing information from and recording information on an opticaldata carrier, such as, e.g., a CD recorder or a DVD recorder. Theprocesses of reproducing information and of recording information arereferred to as reading and writing, respectively. For reading andwriting the light source of the apparatus is generating light ofdifferent intensity and the signal processor of the optical signalreceiving unit is operated in different operating modes. It isadvantageous if programming the control means every time the apparatusis switched from reading to writing or vice versa can be avoided. Tothis end the control signal required for reading and the control signalrequired for writing are stored in the memory device.

When a first program switch signal is provided at the program switchterminal, the control means provides the control signal required forreading. When a second program switch signal is provided at the programswitch terminal, the control means provides the control signal requiredfor writing. The first program switch signal and the second programswitch signal may be, e.g., a relatively high voltage and a relativelylow voltage, respectively.

Alternatively, switching between two or more operating states may beadvantageous in an apparatus equipped with light sources operating atdifferent wave lengths, when the application requires frequent switchingbetween the light sources.

It is advantageous if the optical signal receiving unit is able toreceive an optical signal, which comprises an optical information signalgenerated by the light source and the data carrier, and an opticalprogram signal generated by the light source, and the optical sensorcomprises a first detector for receiving the optical information signaland for providing the optical information signal to the signalprocessor, and a second detector for receiving the optical programsignal and for providing the optical program signal to the controlmeans.

These and other aspects of the optical signal receiving unit and theapparatus according to the invention will be further elucidated anddescribed with reference to the drawings, in which:

FIG. 1 is a schematic drawing of a first embodiment of the opticalsignal receiving unit,

FIG. 2 is a schematic drawing of a second embodiment of the opticalsignal receiving unit,

FIG. 3 is a schematic drawing of a third embodiment of the opticalsignal receiving unit,

FIG. 4 is a schematic drawing of a first embodiment of the apparatus forreproducing information from an optical data carrier,

FIG. 5 is a schematic drawing of a second embodiment of the apparatusfor reproducing information from an optical data carrier, and

FIG. 6 is a schematic drawing of a third embodiment of the apparatus forreproducing information from an optical data carrier.

In the Figures, like reference numerals refer to like parts.

The optical signal receiving unit 10, shown in FIG. 1, has an opticalsensor 20, which in the embodiment of FIG. 1 comprises a photodiode. Theoptical sensor 20 provides the optical signal via electrical lead 22 tothe signal processor 40. The signal processor 40 comprises a sequence ofamplifiers 43, 44, 45 and 46, which amplify the optical signal toproduce a processed signal having an amplitude suitable fortransportation and further processing. The signal processor 40 and theoptical sensor 20 are integrated in the same IC. In another embodimentnot shown the optical sensor 20 is integrated in a first IC and thesignal processor 40 is integrated in a second IC.

The signal processor 40 has an operating mode, which is given amongstothers by the amplification factors of the amplifiers 43, 44, 45 and 46.The amplification factors are determined by control signals provided bya control unit 30. The signal processor 40 provides the processed signalat the output terminal 50. The optical sensor 20 and the amplifiers 43,44, 45 and 46 are provided with electrical power via power terminal 49.

The control unit 30 is programmable by a program signal, which isderived from the processed signal and provided to the control unit 30via electrical lead 27.

In another embodiment not shown the optical signal provided by theoptical sensor 20 is provided directly to the control unit 30.

The optical signal receiving unit 10 further comprises a program controlterminal 51, which enables the control unit 30 to be programmed. Duringnormal operation, when the optical signal receiving unit 10 is used forreceiving an optical signal to be provided at the output terminal 50,the program control terminal 51 is provided with a program controlsignal, which is a relatively low voltage, for example between 0 and 1V.

When the control unit 30 is to be programmed, the program controlterminal 51 is provided with a program control signal, which is arelatively high voltage, for example preferably between 4 and 5.5 V.Upon the change of the program control signal from the relatively lowvoltage to the relatively high voltage, a pulse counter 32, which ispart of a first decoder 31 for decoding the program signal, is reset.The reset is triggered by the edge of the program control signalprovided at the reset terminal 320.

After the program control signal is switched to the relatively highvoltage, the optical sensor 20 is to be provided with a pulsed lightsignal. The corresponding optical signal is processed by the signalprocessor 40 and provided as the program signal to the control unit 30by electrical lead 27. In the embodiment shown in FIG. 1 the operatingmode during programming is equal to the operating mode last used beforeprogramming. In another embodiment not shown the program control signalis provided as control signal to the signal processor 40 duringprogramming.

In the control unit 30 the program signal is first filtered by a lowpass filter 36. In another embodiment, not shown, the filter 36comprises a combination of a low pass filter and a high pass filter, inyet another embodiment also not shown a band pass filter is used.Alternatively, the filter 36 may be omitted. Subsequently, the voltageof the program signal after the low pass filter 36 is compared bycomparator 37 to a reference voltage provided at a reference voltageterminal 370. If the voltage of the program signal is higher than thereference voltage, the comparator 37 provides the voltage of the programsignal via comparator terminal 371 to a first input terminal of an ANDgate 38. A second input terminal of AND gate 38 is provided with theprogram control signal by the program control terminal 51.

When the control unit 30 is programmed and the program control signal isa relatively high voltage, the AND gate 38 is opened by a pulse in theprogram signal and the pulse counter 32 is provided with one pulse. Oncepulse counter 32 has been incremented to the value corresponding to theoperating mode being programmed, the program signal has been decoded andthe pulse counter 32 has a value, which is identical to the decodedprogram signal. The program control terminal 51 is then provided with aprogram control signal, which is a relatively low voltage, for examplebetween 0 and 1 V. Then the pulse counter 32 does not receive any pulsesanymore because the AND gate 38 is closed.

The value of the pulse counter 32 is now stored in a memory device 33,which in the first embodiment shown in FIG. 1 comprises latch 34. Thelatch 34 is loaded with the decoded program signal by edge triggeringupon the change of the program control signal from the relatively highvoltage to the relatively low voltage. Because the triggering is done onthe down going edge of the program control signal, the latter signal isinverted by inverter 340 before being provided to the load terminal 341of the latch 34.

The decoded program signal stored in latch 34 is provided to a seconddecoder 35, which transforms the content of the latch 34 to providecontrol signals to the amplifiers 43-46. In another embodiment, notshown, the optical signal receiving unit 30 further comprises a monitorterminal for monitoring the program signal provided by the AND gate 38.During programming the monitor terminal is coupled to one of the outputterminals of the signal processor 40 so as to allow verification of thesignals during the programming.

In a variation of this embodiment the optical signal receiving unit 10is able to receive a power down signal for switching off the signalprocessor 40. To this end the electrical lead 27 comprises anadditional, e.g. analogous, switch, not shown, which, depending on itsswitching state, is able to electrically connect electrical lead 27 tofilter 36 or to an additional electrical lead, not shown. The additionalelectrical lead is electrically connected to the anode of a photo diodewhich constitutes the optical sensor 20. An additional control lineelectrically connects the second decoder 35 and the switch.

In the power down mode, the amplifiers 43-46 are switched off. When thephoto diode of the optical sensor 20 receives an optical signal and thesignal processor 40 is switched off, the voltage at the entrance of thefirst amplifier 43 increases to a relatively high level due to therelatively high input impedance of the amplifier 43 whereas the voltageat the entrance of the first amplifier 43 is at a relatively low levelwhen the signal processor 40 is switched on. The relatively high voltageat the entrance of amplifier 43 is detected by the additional switch viathe additional electrical lead, the filter 36 ad the comparator 37. Theprogram control terminal 51 is activated and the power down mode isswitched off.

In the second embodiment shown in FIG. 2 the optical signal receivingunit 10 has an optical sensor 20, which comprises a first detector 21for providing the optical signal via electrical lead 22 to the signalprocessor 40. The signal processor 40 is identical to the signalprocessor 40 of the first embodiment described above. The first detector21 is a photodiode, which in another embodiment not shown comprises acentral diode and eight satellite diodes. Each of these diodes providesa signal to a signal processor 40.

In contrast to the first embodiment the optical sensor 20 furthercomprises a second detector 210, which is a photodiode, for providing aprogram signal derived from the optical signal to the control unit 30.The first detector 21 and the second detector 210 are integrated in thesame IC. In another embodiment not shown the first detector 21 isintegrated in a first IC and the second detector 210 is integrated in asecond IC.

The second detector 210 provides the optical signal via electrical lead220 to the signal processor 400. The signal processor 400 comprises asequence of amplifiers 430, 440, 450 and 460, which amplify the opticalsignal to produce a processed signal to a sufficient level. The signalprocessor 400 provides the processed signal at the output terminal 500and via electrical lead 270 to the control unit 30, which is identicalto the control unit 30 of the first embodiment. The signal processor 400has an operating mode, which is given by the amplification factors ofthe amplifiers 430, 440, 450 and 460. The signal processor 400 and thephotodiode 210 are integrated in the same IC. In another embodiment notshown the signal processor 40 and signal processor 400 are integrated inthe same IC.

The amplification factors are determined by control signals from thecontrol unit 30, the corresponding connections are not shown. The seconddetector 210 and the amplifiers 430, 440, 450 and 460 are provided withelectrical power via a power terminal 490.

In another embodiment not shown the amplifiers 430-460 are controlled byseparate control signals by a separate control unit.

In yet another embodiment also not shown the optical signal provided bythe second detector 210 is provided to the control unit 30 without beingprocessed by signal processor 400.

In the third embodiment shown in FIG. 3 the optical signal receivingunit 10 has an optical sensor 20 and a signal processor 40 as describedin the first embodiment. The optical signal receiving unit 10 furthercomprises a monitor terminal 52 for monitoring the program signalprovided by the AND gate 38.

The optical signal receiving unit 10 further comprises a program switchterminal 53 for receiving a program switch signal, which enables thecontrol unit 30 to switch between a first control signal and a secondcontrol signal. The control unit 30 shown in FIG. 3 comprises the filter36, the comparator 37 and the AND gate 38 used in the control unit 30 ofthe first embodiment. The AND gate 38 provides the program signal to thefirst decoder 31, which comprises a synchronous receiver 321. Thesynchronous receiver 321 is provided with a clock signal at a clockterminal, which is not shown.

To enable the control unit 30 to switch between a first control signaland a second control signal, the control unit 30 comprises a logicelement 39 which is provided with the program control signal and theprogram switch signal by the program control terminal 51 and the programswitch terminal 53, respectively. Analogously to the first embodiment,the program control terminal 51 is provided with a program controlsignal, which is a relatively low voltage, for example between 0 and 1 Vduring normal operation, when the optical signal receiving unit 10 isused for receiving an optical signal to be provided at the outputterminal 50.

When programming of the control unit 30 starts, the program controlsignal provided at the program control terminal 51 is changed from arelatively low voltage, for example between 0 and 1 V, to a relativelyhigh voltage, for example between 4 and 5.5 V. Upon the change of theprogram control signal the logic element 39 activates the synchronousreceiver 321 to receive the program signal provided by the outputterminal 382. After synchronous receiver 321 received the entire programsignal, the program control signal provided at the program controlterminal 51 is changed from a relatively high voltage, preferablybetween 4 and 5.5 V, to a relatively low voltage, for example between 0and 1 V.

The program signal received by the synchronous receiver 321 comprises afirst program signal component, in which the first control signal isencoded, and a second program signal component, in which the secondcontrol signal is encoded. The first program signal component and thesecond program signal component are decoded by the synchronous receiver,which provides a first decoded program signal component and a seconddecoded program signal component.

Upon the change of the program control signal from a relatively highvoltage, for example between 4 and 5.5 V, to a relatively low voltage,for example between 0 and 1 V, the logic element 39 provides a firstlatch 345 and a second latch 346 of memory device 33 with a signal toload the first decoded program signal component and the second decodedprogram signal component, respectively. The first decoded program signalcomponent and the second decoded program signal component are stored inthe first latch 345 and the second latch 346, respectively, and providedto the second decoder 35.

When the program switch terminal 53 is provided with a program switchsignal, which is a relatively high voltage, for example between 4 and5.5 V, the logic element 39 provides the second decoder 35 with a signalenabling the second decoder 35 to provide the first control signal tothe amplifiers 43-46.

When the program switch terminal 53 is provided with a program switchsignal, which is a relatively low voltage, for example between 0 and 1V, the logic element 39 provides the second decoder 35 via terminal 350with a signal enabling the second decoder 35 to provide the secondcontrol signal to the amplifiers 43-46.

The apparatus 100 for reproducing information from an optical datacarrier 101 shown in FIG. 4 comprises a light source 102, which is asemiconductor laser. The light source 102 is able to irradiate theoptical data carrier 101, which is a DVD, a CD, CD-R, CD-RW etc. disc togenerate an optical signal, which comprises the information to bereproduced from the optical data carrier 101.

In the first embodiment of the apparatus 100 shown in FIG. 4 the opticalsignal generated by the light source 102 and the optical data carrier101 is received by the optical signal receiving unit 10 shown in FIG. 1and described above.

The apparatus 100 further comprises a system controller 160, which maybe a microprocessor. It controls the intensity of the light source 102by switching the light source 102 on and off to provide the opticalsignal with the information of the program signal. The system controller160 also provides the program control signal to the program controlterminal 51 when the control unit is programmed.

During normal operation, when the optical signal receiving unit 10 isused for receiving an optical signal comprising information from theoptical data carrier 101, the output terminal 50 provides the systemcontrol unit 160 with the processed signal for further processing.

In the second embodiment of the apparatus 100 shown in FIG. 5 theapparatus 100 comprises an optical signal receiving unit 10 as shown inFIG. 2. During normal operation the optical signal comprises an opticalinformation signal, which is generated by the light source 102 and theoptical data carrier 101. When the control unit 30 is programmed theoptical signal comprises an optical program signal generated byswitching on and off the light source 102. The switching on and off iscontrolled by the system control unit 160 The optical sensor 20comprises a first detector 21, which receives the optical informationsignal and provides it to the signal processor 40. The optical sensor 20further comprises a second detector 210, which is provided with theoptical signal by a semi-reflecting surface of a beam splitter 106. Thesecond detector 210 receives the optical program signal and provides itto the control unit 30 via electrical lead 270.

In the third embodiment of the apparatus 100 shown in FIG. 6 theapparatus 100 comprises an optical signal receiving unit 10 shown inFIG. 3. The apparatus 100 is a DVD recorder which is able to recordinformation on the optical data carrier 101 which is recordable DVDdisc. When the apparatus 100 records information in the optical datacarrier 101, the light source 102 is operated at relatively high power.The optical signal is then processed by the signal processor 40 using arelatively low amplification factor corresponding to a first controlsignal. When the apparatus 100 reproduces information from the opticaldata carrier 101, the light source 102 is operated at relatively lowpower. The optical signal is then processes by the signal processor 40using a relatively high amplification factor corresponding to a secondcontrol signal. The power of the light source 102 is controlled by thesystem control unit 160.

Referring to FIG. 3, the first control signal and the second controlsignal are stored in the first latch 345 and the second latch 346,respectively. The system control unit 160 shown in FIG. 6 is connectedto the program switch terminal 53 to switch the control unit 30 betweenthe first control signal and the second control signal.

The optical signal receiving unit 10, which receives and processes anoptical signal, can be programmed by the optical signal. The opticalsignal is detected by an optical sensor 20 and processed by a signalprocessor 40. The signal processor 40 has an operating mode, which isset by a programmable control unit 30. The control unit 30 isprogrammable by a program signal derived from the optical signal. In oneembodiment the optical signal receiving unit 10 can be switched betweentwo operating modes by a program switch signal provided at a programswitch terminal 53. The apparatus 100 for reproducing information froman optical data carrier 101 comprises an optical signal receiving unit10 according to the invention.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.The word “comprising” does not exclude the presence of other elementsthan those listed in a claim. The word “a” or “an” preceding an elementdoes not exclude the presence of a plurality of such elements. Theinvention can be implemented by means of hardware comprising severaldistinct elements, and by means of a suitably programmed computer. Inthe device claim enumerating several means, several of these means canbe embodied by one and the same item of hardware. The mere fact thatcertain measures are recited in mutually different dependent claims doesnot indicate that a combination of these measures cannot be used toadvantage.

1. An optical signal receiving unit (10) comprising: an optical sensor(20) for receiving optical signals including an optical informationsignal and an optical program signal, control means (30) for providing acontrol signal in dependence on said optical program signal, and asignal processor (40) for processing at least the optical informationsignal to produce a processed signal, the signal processor (40) havingan operating mode set by the control signal.
 2. An optical signalreceiving unit (10) as claimed in claim 1, further comprising a programcontrol terminal (51) for receiving a program control signal to enablethe control means (30) to be programmed by a program signal derived fromthe optical program signal.
 3. An optical signal receiving unit (10) asclaimed in claim 1, wherein the control means (30) comprise a firstdecoder (31) for decoding the optical program signal to provide adecoded program signal.
 4. An optical signal receiving unit (10) asclaimed in claim 3, wherein the first decoder (31) comprises a pulsecounter (32).
 5. An optical signal receiving unit (10) as claimed inclaim 3, wherein the control means (30) further comprise a memory device(33) for storing and providing the decoded program signal.
 6. An opticalsignal receiving unit (10) as claimed in claim 5, wherein the controlmeans (30) further comprise a second decoder (35) for further decodingthe decoded program signal provided by the memory device (33) to providethe control signal.
 7. An optical signal receiving unit (10) as claimedin claim 1, wherein the optical sensor (20) comprises: a first detector(21) for providing the optical information signal to the signalprocessor (40), and a second detector (210) for providing a programsignal to the control means (30), the program signal being derived fromthe optical program signal.
 8. An optical signal receiving unit (10) asclaimed in claim 1, further comprising a monitor terminal (52) formonitoring the optical program signal.
 9. An optical signal receivingunit (10) as claimed in claim 5, wherein: the control means (30) is ableto provide a first control signal and a second control signal as thecontrol signal, the signal processor (40) has a first operating mode setby the first control signal and a second operating mode set by thesecond control signal, and the optical signal receiving unit (10)further comprises a program switch terminal (53) for receiving a programswitch signal enabling the control means (30) to switch between thefirst control signal and the second control signal.
 10. An apparatus(100) for reproducing information from an optical data carrier (101),the apparatus (100) comprising: a light source (102) for irradiating theoptical data carrier (101) to generate an optical signal, an opticalsignal receiving unit (10) as claimed in claim 1, system controllingmeans (160) for controlling the light source (102) and for furtherprocessing the processed signal.
 11. An apparatus (100) as claimed inclaim 10, wherein: the optical information signal is generated by thelight source (102) and the optical data carrier (101), and the opticalprogram signal is generated by the light source (102), and the opticalsensor (20) comprises: a first detector (21) for receiving the opticalinformation signal and for providing the optical information signal tothe signal processor (40), and a second detector (210) for receiving theoptical program signal and for providing the optical program signal tothe control means (30).